In a compressor, low momentum flow along the outer shroud of the compressor is known to be detrimental to the aerodynamic performance or to trigger premature rotor stall. Accordingly, bleeding such low momentum air flow at the shroud is performed to improve engine performance and operability.
Further, recirculation and reintroduction of the air which bled off back into the compressor flow has been found advantageous to improve the stall margin of the compressor. However, stall margin improvement by such known recirculation systems typically comes at the expense of performance loss. Improvement is therefore sought.